Automatic thermal crown control of strip mill rolls

ABSTRACT

A SYSTEM FOR CONTROLLING THERMAL CROWN OF STRIP MILL ROLLS. THICKNESS VARIATIONS OR OFF-FLATNESS OF THE ROLLED STRIP ARE SENSED AT A PLURALITY OF ZONES ACROSS THE STRIP, AS WELL AS EXCESSIVE BENDING FORCES AT THE ROLL JACKS. ZONES INSIDE THE EDGES OF THE STRIP ARE CONTROLLED PRIMARILY IN ACCORDANCE WITH THICKNESS VARIATIONS OR OFF-FLATNESS, WHILE ZONES OUTSIDE THE EDGES OF THE STRIP ARE CONTROLLED PRIMARILY IN ACCORDANCE WITH EXCESSIVE BENDING FORCES. ZONES AT THE EDGES OF THE STRIP ARE MANUALLY CONTROLLED. MANUAL AND AUTOMATIC CONTROL MAY BE CONCURRENTLY UTILIZED. PROVISION IS MADE TO ENSURE THAT COOLANT FLOWS ARE NOT CHANGED WITHIN A PREDETERMINED TIME FOLLOWING A PRECEDING CHANGE, EXCEPT FOR CHANGES IN ACCORDANCE WITH EXCESSIVE BENDING FORCES AT THE ROLL JACKS. THE DETECTION OF MAXIMUM AND MINIMUM STRIP THICKNESSES OR CONDITIONS OF OFF-FLATNESS FOR BOTH ZONES TO WHICH COOLANT IS BEING SUPPLIED AND ZONES TO WHICH NO COOLANT IS BEING SUPPLIED IS UTILIZED WITH COOLANT FLOWS BEING VARIED TO THESE PARTICULAR ZONES.

United States Patent [72] Inventor 0livoG.Slvllotti Kingston, Ontario, Canada [21 Appl. No. 788,705 [22] Filed In. 3, 1969 [45] Patented June 28, 1971 [731 Assignee Alcon Research and Development Limited.

Montreal, Quebec,

[54] AUTOMATIC THERMAL CROWN CONTROL OF LOAD CELL R5400! 3,475,935 11/1969 Kajiwara 72/9 3,496,744 2/1970 Mizunoetal 72/12 Primary Examiner-Milton S. Mehr Attorneys-Robert S. Dunham, P. E. Henninger, Lester W. Clark, Gerald W. Griffin, Thomas F. Moran, Howard J. Churchill, R. Bradlee Boal, Christopher C. Dunham and Robert Scobey ABSTRACT: A system for controlling thermal crown of strip mill rolls. Thickness variations or off-flatness of the rolled strip are sensed at a plurality of zones across the strip, as well as excessive bending forces at the roll jacks. Zones inside the edges of the strip are controlled primarily in accordance with thickness variations or off-flatness, while zones outside the edges of the strip are controlled primarily in accordance with excessive bending forces. Zones at the edges of the strip are ,manually controlled. Manual and automatic control may be concurrently utilized. Provision is made to ensure that coolant flows are not changed within a predetermined time following a preceding change, except for changes in accordance with excessive bending forces at the roll jacks. The detection of maximum and minimum strip thicknesses or conditions of off-f1atness for both zones to which coolant is being supplied and zones to which no coolant is being supplied is utilized with coolant flows being varied to these particular zones.

DTH

COMP/124704 5515C FF ZONES GOA IP04 LOG/C UAl/T 5 FEED SIGN/71.

SHEET 1 BF 5 PATENTEU JUN28 ISYl PATENTED JUN28 1971 SHEET 2 OF 5 w MQON PATENTED JUH28 I971 SHEET 3 BF 5 AUTOMATIC THERMAL CROWN CONTROL OF STRIP MILL ROLLS BACKGROUND AND BRIEF DESCRIPTION OF THE INVENTION This invention relates to the control of thermal crown of strip mill rolls. More particularly it is directed to the control of a heat exchange medium such as a coolant supplied to the strip mill rolls to vary thermal crown in accordance with detected strip thickness variations or off-flatness conditions, i.e., in accordance with variations in strip contour. The invention also relates to control systems generally, and is directed to the control of a variable factor in a process in accordance with a monitored condition.

Thermal crown of strip mill rolls has been controlled in the past by the variation of oil flow to the rolls in accordance with variations in strip thickness. Pearson US. Pat. No. 3,078,747, issued Feb. 26, I963, discloses such a system. In the present invention thickness variations or conditions of off-flatness are sensed at a plurality of zones across the strip, and the flow of a heat exchange medium such as a coolant to corresponding zones of the strip mill rolls in accordingly controlled. In this fashion many areas over the complete surface of the rolls may be individually controlled as to thermal crown.

The present invention contemplates the separation of the zones into two groups, namely, zones to which coolant is currently being supplied and zones to which coolant is current not being supplied. The maximum and minimum strip thicknesses or condition of off-flatness in each of these two groups of zones are determined and are utilized as controlling factors determining the flow of coolant to various zones. In this fashion, the zones corresponding to the extremes of strip thickness or off-flatness are controlled specifically by changing the flows of coolant thereto so as to properly adjust the thermal crown of the rolls and to render the strip flat and of uniform thickness.

Additionally, the invention contemplates distinguishing between zones inside the edges of the strip and zones outside the edges of the strip. For zones inside the edges of the strip the control of coolant primarily may be in accordance with strip thickness variations or off-flatness, while for zones outside the edges of the strip the flow of coolant may be primarily in accordance with excessive bending forces at the roll-jacks, either positive or negative. Zones at the edge of the strip may be manually controlled at such time.

All or selected ones of the zones may be placed on manual control as the need arises.

Accordingly, an object of the invention is to provide for the control of thermal crown of strip mill rolls.

A further object of the invention is to provide for the control of thermal crown in accordance with strip thickness variations or off-flatness, i.e., with respect to contour variations.

Another object of the invention is to provide for the control of thermal crown, in accordance with excessive bending forces.

The present invention is also directed generally to the control of a variable factor in a process in accordance with a monitored condition. In particular, in any control system in which a condition is sensed for each of a plurality of zones in which an action is taken, for example, an on-off" action in which coolant is being supplied or not supplied, the zones are classified into a group of on zones and a group of off zones, and the status of one or more zones is switched from one group to the other depending upon the sensed condition of that zone. Extremes of the sensed conditions may be noted and changes in on"-oft actions made in accordance therewith so that the two groups bear a particular relationship to each other. For example, the off" zones may be made to exhibit higher values of the sensed condition than the on" zones. In this fashion the ranges of condition variations of "off" and on" zones may be desirable reduced.

Accordingly, an object of the invention is to provide for the control of a system of variable factors in accordance with the monitored condition of each of the factors.

These and other objects of the invention as well as further specific details of the control techniques will be more completely understood by reference to the following detailed description, which is to be read in conjunction with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a block diagram of a system for controlling the thermal crown of strip mill rolls in accordance with the invention.

FIG. 2 is a perspective view showing representative strip mill rolls.

FIGS. 3 and 4 are schematic circuit diagrams (partially in block form) of various parts of the control system of FIG. 1.

FIGS. 5 and 6 are block diagrams of further parts of the control system of FIG. 1.

DETAILED DESCRIPTION FIGS. 1 and 2- Referring to FIGS. 1 and 2, the invention is illustrated as applied to a 4-high mill 10. The mill includes upper and lower backup rolls 12 and 14 having their necks or shafts respectively carried in conventional chocks (not shown) and arranged to bear on upper and lower work rolls l6 and 18, which in turn are carried at their necks or shafts by conventional chocks (not shown). The entire assembly is supported in a usual frame or housing (not shown) with conventional screwdowns indicated schematically at 22 and bearing on the upper backup roll chocks, with appropriate gearing or like drive as indicated at 23 for adjusting the pressure applied by the screwdowns to the rolls. It should be understood that many parts of conventional strip mills have been omitted from FIG. 1 for the purpose of clarity.

In FIG. 1 balance jacks 28 are interposed between the upper and lower work roll chocks, while contour jacks are similarly interposed between the work roll chocks and the upper and lower backup roll chocks. Specifically, contour jacks 30 are interposed between the upper work and backup roll chocks, and contour jacks 31 are interposed between the lower work and backup roll chocks. All of these jacks may be of known, conventional construction and involving rugged hydraulic cylinders with heavy plungers (not shown) arranged to exert force between the associated roll chocks upon introduction of hydraulic fluid under pressure. Specifically, a fluid supply 39 supplies hydraulic fluid to the upper and lower contour jacks 30, 31 via conduits 40, 41, joining in a common conduit 42, and to the balance jacks 28 via conduit 44. FIG. 1 indicates, for simplicity, a single jack on each side at each location.

This complete system of jacks applies bending forces to the work rolls. Thus if the pressure of the contour jacks predominates, the ends of the work rolls tend to be bent toward each other, as to overcome a thermal crown of the rolls, or to create a crowned roll gap between what might otherwise be parallel roll surfaces, while predominance of pressure in the balance jacks, over the contour jacks, tends to bend the work rolls away from each other at their ends, as for example where desired to overcome a crowd or bulging roll gap that would otherwise exist. The rolling load may be sensed by load cells 60 positioned, e.g., between the lower backup roll chocks and the base or frame of the mill. The load cells supply signals to load cell readout circuit 62 to provide an indication of the rolling load.

The entire assembly is maintained under a rolling pressure for the desired production of metal strip 35 traversing the bite of the work rolls 16 and 18 by the screwdowns 22. The strip to be rolled is supplied from a coil (not shown) provided with appropriate drag or mechanical resistance to maintain a back tension on the portion of the strip 35a traveling to the work rolls, while the strip of desired reduced gauge traveling from the mill, as at 35b, is rewound in a coil (not shown) after passing over a billy roll 70. The billy roll includes means for sensing the stresses created therein by the strip at various zones in the roll. The stress in each zone is dependent upon the tension in the strip at that zone and accordingly is representative of the thickness and flatness of the strip at the zone. The bill roll may be of the type disclosed in Sivilotti Pat. No. 3,324,695, issued June 13, 1967, e.g., including a helically positioned sensing element, or may be of the type disclosed in French Pat. No. l,495,722 in which a plurality of individual sensing elements are employed. In any event, signals developed at slip rings 72-1, 72-2...72-n are representative of stresses sensed in the billy roll for zones 1, 2...n across the billy roll as created by the strip 35 bearing against the billy roll. These signals representing strip thickness and flatness are applied to signal gates 1, 2...n as shown in FIG. 1 forming part of a control system that controls the flow of a heat exchange medium, specifically a coolant to the strip mill rolls.

In particular, a coolant such as oil from a coolant supply 74 is supplied by conduits 76-1, 76-2...76-n and through valves V1, V2...n to spray heads for spraying the coolant onto the strip mill rolls. As shown in FIGS. 1 and 2, spray heads 78-1, 78-2...78-n are positioned above the strip 35 and supply coo; lant to the upper backup roll 12 and work roll 16, while spray heads 80-1, 80-2...80-n are positioned below the strip 35 apd spray coolant onto the lower work roll 18 and backup roll M. The spray heads, shown schematically in H65. 1 and 2, are supplied coolant individually from the valves V1, V2...Vn. The system of FIG. 1 controls the valves V1, V2... Vn by signals on conductors designated 82 from a control logic unit 84. As will be explained in more detail below, the valves are controlled automatically to selectively supply coolant to various zones in accordance with detected strip tension at the billy roll, which is directly related to strip contour, i.e., strip thickness and flatness, as well as in accordance with excessive bending forces at the balance jacks 28 and contour jacks 30 and 31.

In the embodiment shown in FIG. 1, thermal crown is controlled by supplying a liquid coolant to the work rolls. Other methods of controlling thermal crown could be employed. For example, radiant or induction heaters (not shown) spaced across the rolls could provide heating of the roll zones. in such a case then, supplying of heat corresponds to discontinuance of coolant flow, and removal of heat corresponds to supplying of coolant. Regardless of the actual technique employed, the control of thermal crown is achieved through control over the supply of a heat exchange medium to the various zones of the rolls.

To explain the basic control system of FIG. 1 in more detail, it includes pressure sensors 86 and 88 which sense respectively the fluid pressures supplied to the balance and contour jacks. For this purpose, conduits 44a and 42a, constituting extensions of the fluid supply conduits 44 and 42, may be used to detect these jack pressures. The pressure sensors 86 and 88 develop signals which are supplied to a comparator 91), which develops a signal at an output conductor 92 whenever excessive positive bending force occurs. That is, in the event that the pressure in the balance jacks predominates over the pressure in the contour jacks by more than a predetermined amount, indicating excessive positive bending force, a signal is developed on the conductor 92. Similarly in the event that the pressure in the contour jacks predominates over the pressure in the balance jacks by more than a predetermined amount, the comparator 90 senses this condition and generates a signal on conductor 94 representing excessive negative bending force. These signals are applied to the control logic unit 84 to develop signals applied to the valves V1, V2...Vn to vary the flow of coolant to selected zones so as to reduce the excessive bending forces. In particular, it has been determined that a desirable mode of control is to vary the zones outside the edges of the strip in accordance with excessive bending force. Accordingly, in the system of FIG. 1 a width zone selector unit 96 generates signals applied to the control logic unit 84 that indicate, for a strip of a particular width, those zones which are inside the edges of the strip and those zones which are outside the edges of the strip. The control logic unit develops signals on the conductors 82 that control the coolant supply valves so that coolant supply is only varied for those zones outside the edges of the strip to correct for the excessive bending force at the roll jacks. lf excessive positive bending force is encountered, coolant is supplied to zones outside the edges of the strip. lf excessive negative bending force is encountered, coolant is not supplied to such outside zones.

It is contemplated that such control of coolant to the outside zones in accordance with excessive bending forces ex erted by the roll jacks will take place only when the roll jacks are themselves controlled in accordance with rolling load. Such control of the roll jacks is disclosed in Sivilotti et al. application, Ser. No. 7l 3,150, filed Mar. 14, 1968, No. 3,534,571, issued Oct. 20,1970 for Rolling Mill Control, assigned to the assignee of the present application. A signal source 97 in FIG. 1 and designated auto roll deflection control represents the control of roll jacks in accordance with rolling load. When such control is taking place, a signal is generated by the source 97 which is applied to the control logic unit 84, permitting that unit in turn to control coolant flow to the outside zones in accordance with excessive bending forces exerted by the roll jacks.

It is contemplated that the flow of coolant to the zones inside the edges of the strip will be controlled in accordance with the strip tension detected in the hilly roll for these zones. The signal gates 1, 2...n, passing the strip tension signals from the billy roll 70, are controlled by signals from the conductors 82. Specifically, all those signal gates corresponding to zones in which coolant is being supplied (i.e., the valves are open) are controlled so as to pass the billy roll signals to an on" zones discriminator 98. Similarly, the signal gates are controlled by signals on the conductors 82 so that all gates corresponding to zones in which no coolant is being supplied (i.e., the valves are closed) pass the billy roll tension signals to an of zones discriminator 100.

The on zones discriminator 98 develops two signals on output conductors 102 and 1104, representing respectively the maximum or highest potential signal applied to the discriminator and the minimum or lowest potential signal applied to this discriminator. in other words, the on" zones discriminator develops two signals representing the maximum and minimum tensions in the strip 35 detected for all those on zones in which coolant is being supplied. Similarly, the off" zones discriminator develops on output conductors 106 and 108 signals respectively representative of the maximum or highest potential and minimum or lowest potential input signals to the discriminator. In other words, the on" zones discriminator 100 develops signals representing the highest and lowest tensions in the strip 35 sensed by the billy roll for those zones in which no coolant is being supplied. The signals on the conductors 102, 104, 106 and 108 are applied to the control logic unit 84.

The on" zones discriminator 98 also develops signals on conductors 110-1, 110-2...110-n that are supplied to the control logic unit 84. Similarly the of zones discriminator 100 develops si nals on conductors, 112-1, 112-2...112-n that are supplied to the control logic unit. Each of the conductors 110 and 112 corresponds to one of the zones 1, 2...n and provides a connection through the control logic unit to the output conductors 82-1, 82-2...82-n controlling the coolant supply valves V1, V2...Vn. The control logic unit 84 also receives a speed signal from a source 114 representing a strip speed through the mill rolls that is greater than a predetermined speed (S feet per minute). Alternatively, the source 114 may generate a timing signal indicating that a minimum delay time has passed since the initiation of a rolling operation. In any event, the source 114 provides a signal representing a rolling operation in effect. Further, a control unit 116 supplies signals to the control logic unit 84 to determine whether the latter unit is under automatic or manual mode of operation, for all or selected ones of the zones. It is contemplated, as noted abovefto provide manual control for the flow of coolant to zones at the edge of the strip, in any event. Other zones, as desired, may also be placed under manual control.

Within the control logic unit 84 signals are developed on the conductors 82 to control the flow of coolant to those zones inside the edges of the strip in accordance with the strip tensions detected in the billy roll 70 corresponding to these zones, par ticularly in accordance with the maximum and minimum strip tensions as sensed by the on and "off" zones discriminators 98 and 100 as influenced by the signals from the signal source 114.

FIGS. 3-5

FIGS. 3 to 5 show the details of a representative control system as will now be explained. FIGS. 3 and 4, to be explained first, respectively show the details of representative embodiments of the ofF and on" zones discriminators 100 and 98. FIG. 5 shows the details of part of a representative control system to develop on" and off trigger pulse signals utilized respectively to switch coolant valves from a closed to an open position and from an open to a closed position. FIG. 6 shows the details of another part of a representative system for use in conjunction with the on" and ofP' trigger pulse signals for developing suitable control signals and channeling them to appropriate ones of the coolant supply valves V1, V2...Vn.

FIG. 3

Referring to FIG. 3, which shows the off" zones discriminator, the circuit provided detects the highest and lowest voltages supplied thereto from the billy roll. These voltages represent the highest and lowest strip tensions detected in the billy roll for all of the off" zones, i.e., for all of the zones to which no coolant is being supplied. The input signals to the circuit of FIG. 3 are supplied by the signal gates 1,2...n shown in FIG. 1. These signals are applied to the bases ofa first series of transistors 120-1, 120-2...]20-n and to the bases of a second series of transistors 122-1, 122-2. 122-n. The first series of transistors 120 selects the highest ofF signal applied to the bases thereof, while the second series of transistors 122 selects the lowest off signal applied to the bases thereof. In particular, the transistors 120 may be of the NPN-type, the collectors of which are connected through individual resistors 124-1, 124-2 ...124-n to a suitable biasing potential of +V volts. The emitters of this series of transistors are all coupled through a single common emitter resistor 126 to a source of negative biasing potential of V volts. That one of the transistors 120 which has the highest or most positive base potential will conduct, in effect coupling that base potential through its emitter to common emitter conductor 128. All of the other transistors 120 supplied with "ofP signals will be reverse biased because the common emitter potential of the conductor 128 is more positive than the base potentials of these other transistors. The signal on the common emitter conductor 128 is amplified by an amplifier 130 and applied to an output terminal 132. The signal at this terminal represents the highest or most positive signal received from the off zones in the billy roll 70 of FIG. 1, i.e., it represents that zone having the highest strip tension of all the off" zones to which coolant is not being supplied.

The transistors 122 select the lowest potential, as noted above. In particular, the transistors of the series may be of the PNP type, the collectors of which are connected through resistor voltage dividers 134-1 and 136-1, 134-2 and 136-2...l34C-n and 136-1 to the source of negative potential of V volts. Each of the resistor voltage divider combinations 134 and 136 corresponds to the individual resistors I24 coupled to the transistors 120 just described. The voltage division is employed for the purpose of signal amplification, as will be described. The emitters of all of the transistors 122 are connected through a common emitter resistor 138 to the positive potential source of +V volts. Accordingly that one of the transistors 122 which has the lowest or most negative base potential is rendered conductive, in effect coupling that most negative base signal to common emitter conductor 140. All of the other transistors of the series supplied with off" signals will be reverse biased, since the common emitter potential is more negative than the base potentials of these other transistors. The signal on the common emitter conductor is amplified in amplifier 142, whose output is connected to output terminal 144. The signal at the output terminal 144 is thus representative of the smallest detected signal from the ofF zones in the billy roll 70, i.e., it represents the lowest strip tension for all of the off zones to which coolant is not being supplied.

The off zones discriminator is employed to provide an output signal used in conjunction with other signals to turn the coolant on" in the appropriate one of the zones currently in the off condition. To this end a series of amplifiers consisting of transistors 146-1, 146-2...146-n is employed (e.g. NPN-type). The bases of the transistors 146 are coupled through individual base i esistors 148-1, 148-2...148-n to the junction point of the corresponding voltage dividing resistor networks 134 and 136. The emitters of these transistors are all connected directly to the source of negative potential of -V volts, while the collectors are connected to the positive source of potential of +V volts through corresponding collector resistors 150-1, 1502...150n. That one of the amplifiers 146 corresponding to the particular transistor 122 which is conducting generates an output signal at the corresponding one of output terminals 152-1, 152-2...l52-n. In particular, the transistor 122 which is conducting causes an increase in the potential at the junction point between the corresponding resistors 134 and 136 over that which is present at the junction point when the transistor is not conducting, i.e., an increase from a negative signal to a more positive signal. This positive increase in potential at the junction point of the resistors 134 and 136 is communicated through the corresponding one of resistors 148 to the base of the corresponding transistor 146. The base is rendered more positive than the emitter, rendering the transistor conductive, which lowers the potential of the corresponding output terminal 152 essentially to the negative biasing potential of V volts through the coupling of the emitter to the collector. When the transistor 146 is nonconductive, on the other hand, the potential of the output terminal 152 is at the higher biasing potential of +V volts. Accordingly, a negative signal of approximately -V volts appears at that one of the terminals 152 corresponding to the zone presently in the off condition which has the least strip tension and to which coolant will be supplied if other conditions are met, to be explained below.

The circuit of the off zones discriminator includes a feature to render all those transistors nonconductive corresponding to zones in the on state. In particular, a pair of resistors 154 and 156 are connected across the outputs of the amplifiers 130 and 142. The junction point of these resistors is connected to an amplifier 158 which provides an output signal at conductor 160 representing some voltage (termed a parking voltage) between the highest and lowest off zone voltages. The conductor 160 is coupled to the bases of both series of transistors and 122 through resistors 162-1, 1622...162n. For all of the zones which are currently inth e on" condition there will be no signals present from the signal gates 1, 2...nthat are connected to the off zones discriminator. Hence the parking voltage from the conductor 160 is coupled through the corresponding ones of the resistors 162 to the bases of the transistors 120 and 122 of all these zones currently in the on condition. Since the parking voltage is between the highest and lowest off zone voltages, these transistors corresponding to on zones are effectively prevented from being triggered into conduction. The parking voltage does not interfere with signals from the signal gates 1, 2...n corresponding to all zones currently in the of condition, since the resistance of resistors 162 is chosen high. These 011" signals will thus be communicated to the bases of the transistors 120 and 122. Only when signals are not present can the parking voltage from the conductor 160 be communicated to the bases of the transistors.

FIG. 4

The on" zones discriminator 98, as shown in FIG. 4, is similar to the zones discriminator of FIG. 3. The input signals to the circuit are derived from the signal gates 1, 2,..n, a signal being present on an input conductor when the corresponding zone is in the "on" condition, i.e., when coolant is being supplied to the zone. The signal gates are connected to the bases of afirst series of transistors170-1, 170-2. .170-n and to the bases of a secoi'id series of transistors 172-1, 172-2. 172 1 l 5 of V volts. The transistor having the most negative base potential is rendered conductive, in effect applying this most negative base potential to common emitter conductor 178. All of the other transistors supplied with on signals are rendered nonconductive, since the base potentials thereof are more positive than the common emitter potential. The signal on conductor 178 is amplified in an amplifier 180 which produces a signal at output terminal 182 corresponding to the lowest on" zone voltage. This voltage represents that one of the on zones to which coolant is being supplied and experiencing the least strip tension.

The second series of transistors 172 is similar to the second series of transistors 122 of FIG. 3. In this case, however, the transistors 172 (e.g. NPN-type) select the highest base potential supplied thereto. The emitters of transistors 172 are all connected through a common emitter resistor 184 to the source of negative biasing potential of V volts. The collectors of these transistors are connected through resistor voltage dividing networks 186-1 and 188-1, 186-2 and 1ss-2'...1s6-n.

and 188-): to the source of positive biasing potential of +V volts. The transistor 172 having the highest base potential is rendered conductive coupling that base potential to common emitter conductor 190. All of the other transistors supplied with "on" signals are rendered nonconductive since this common emitter potential is here than the base potentials of these Thus a relatively positive output signal is provided at the output terminal 202 corresponding to the on" zone having the highest strip tension. This signal is employed in conjunction with other signals to turn the coolant "off" in that particular zone.

The on" zones discriminator of FIG. 4 also includes a parking voltage feature as in the off zones discriminator. In particular, the highest and lowest on zone voltages as amplified by the amplifiers 192 and 180 are coupled to a voltage divider network consisting of resistors 210 and 212. The junction point of these resistors is connected to an amplifier 214 which generates a parking" voltage at conductor 216, which parking" voltage is between the highest and lowest on zone voltages. The conductor 216 is coupled through resistors 21 1 1. 2!. i-.. tub b es. 9f. he. WQ L ...9 transistors 170 and 172. The parking" voltage is effectively coupled to all those transistors of these two series in which no signals are present from the signal gates l, 2...n. In other words, the parking voltage is communicated to the bases of all transistors corresponding to off zones in which coolant is not being supplied, since signals are not present on the on" conductors from the signal gates. This intermediate "parking voltage between the highest and lowest on" zone voltages ensures that these transistors corresponding to off" zones remain nonconductive.

FIG. 5

cuit of FIG. 5 is explained, however, the following table should other transistors. The signal on the conductor 190 is amplified in amplifier 192 so as to generate at output terminal 194 a signal representing the highest or most positive on" zone voltage.

he "9" diss i i a prinslud s risa,9flamp ifie's. comprised of transistors 196-1, 1962...196-n which serve to provide an output signal corresponding to the "on" zone experiencing the highest strip tension. The transistors 196 are coupled throughbase resistors 198-1, 198-2...198-n to the junction points of the corresponding resistor voltage dividing networks 186 and 188. The emitters of these transistors are connected directly to the source of positive biasing potential of +V yolts, while the collectors are connected through individual resistors 200-1, 200-2...200-n to the source of negative biasing potential of V volts. The collectors of these transistors are connected to output terminals 202-1,

202-2.:202-1 The output terminals 202 are'TidifiiEfiYEfiii be considered, which describes the operating logic of the system. Specifically, the conditions for change are enumerated, and the action to be taken dependent upon those conditions is given.

OPERATING LOGIC Total off-flatness exceeds a predetermined valve F.

Strip speed exceeds S feet per minute; or a minimum delay time has elapsed since the commencement of a rolling operation.

Conditions The highest strip tension of the coolant on zones is greater than the lowest strip tension. of the coolant off zones, or the difference between the ranges of off-flatness of the on and off zones exceeds X.

A previous change has not been made within a cycling time delay period.

A zone in which a change is to be made is inside the edge of the strip.

Action Change from coolant off to coolant on" in that coolant ofizone experiencing the least strip tension if the range of off-flatness in the coolant off zones exceeds the range of off-flatness in the coolant on" zones; or change from coolant on" to coolant off in that coolant on" zone experiencing the greatest strip tension if the range of off-flatness in the coolant on zones exceeds the range of off-flatness in the coolant off zones.

Condition Excessive negative bending force exerted by the roll jacks, which are under control in accordance with rolling load.

Action Turn coolant ofi in selected zones outside the edge of the strip.

Condition Excessive positive bending force exerted by the roll jacks, which are under control in accordance with rolling load.

Action Turn coolant on" in selected zones outside the edge of the strip.

Before the specific operating logic given in the above table is explained, it should be mentioned that the system is designed with the criterion in mind that the strip tensions of all the coolant off zones should be higher than all the strip tensions of the coolant on" zones. Thus the strip tension signals from the billy roll should result in two groups of signals, namely, a first group of signals from all the off" zones which are of greater magnitude than all the signals from the on" zones. It

will also be helpful to note that in the event that a part of a mill roll is of greater diameter than it should be, such a condition I results in a smaller gauge of strip at this section, in turn leading to a longer length of strip, which in turn results in a smaller tension in the corresponding billy roll zone and a smaller billy roll signal for this zone. The correction is to supply more coolant to this zone to reduce the diameter of the roll.

In the system of operating logic, the total off-flatness of the strip, i.e. the difference between the highest and lowest strip tensions, is given by the difi'erence between the maximum strip tension signal from the off" zones and the minimum strip tension signal from the on" zones (since the signals from the off" zones are to exceed the signals from the "on" zones). Changes that are made are achieved with respect to extremes in the on" and ofi zones. Particularly, the "off" zone exhibiting the smallest strip tension signal will be changed to an "on" zone, or an on" zone exhibiting the highest strip tension signal will be changed to an off zone in the event that a change is deemed necessary. Changes are deemed necessary, among other criteria, in the event that the maximum strip tension signal from the on" zones is greater than the minimum strip tension signal from the off" zones. This indicates that the ranges of signals from the on" and oil zones are not proper, since all "off" zones should exhibit higher signals than on" zones. It will be seen that the system operates to change that extreme one of the zones of the "on" or off group closest to the range defined by the other group of zones whenever there is an overlap condition. The zone changed is that one of the extreme zones belonging to the group of zones exhibiting the greater variation of strip tension signals.

The control of the flows of coolant to the various zones may be made dependent upon difierent operating conditions. In the representative embodiment described herein, the conditions for automatic action are given in the above table. It has been deemed desirable to make a coolant change whenever the total off-flatness of the strip exceeds a predetermined value F. The total off-flatness is represented by the difference between the highest and lowest strip tensions as sensed by the hilly roll. It has also been determined that changes should be automatically made only when the speed of the strip passing through the rolls exceeds S feet per minute, or after a delay following initiation of a rolling operation sufficient for the billy roll 76 to develop reliable signals of strip tension. Another criterion is that the highest strip tension as sensed by the hilly roll for the coolant"on" zones is higher than the lowest strip tension as sensed for the coolant ofi zones. An alternative criterion is that the difference between the ranges of off-flatness exceeds some predetermined value X. The ranges of off-flatness are represented by the difference between the highest and lowest strip tensions for the coolant "on" zones, on the one hand, and the difference between the highest and lowest strip tensions for the coolant off zones, on the other hand. An additional criterion is that a previous change has not been made within a cycling time delay period, which is an arbitrary period established as a minimum time that should elapse between successive changes. Finally, the last criterion as set forth in the table is that the zone in which a change is to be made is inside the edge of the strip.

If the above criteria are met, the flow of coolant is turned "on in the zone previously off" having the least strip tension as sensed by the billy roll. This change will take place if the range of off-flatness in the coolant off zones exceeds the range of off-flatness in the coolant on" zones. In other words, this particular change is made if the difference in strip tensions as sensed by the billy roll for the coolant off zones exceeds the difference for the coolant on" zones, indicating that the strip tension varies to a much greater degree of the coolant off" zones. in such a case more zones should be brought to the coolant on" state, and this is the change which takes place. In particular, that one of the coolant off zones closest to the on" zones in magnitude of strip tension signal is changed to the on" state.

On the other hand, if the above conditional criteria are met, a change is made to switch of the coolant flow in a zone to which coolant was previously supplied if that zone is sensed as having the greatest strip tension of all coolant on" zones and if the range of off-flatness in coolant on zones and if the range of exceeds the range of off-flatness in the coolant of zones. In other words, this particular change is made in the event that the strip tension in the on" zones varies by a greater amount than the strip tension in the coolant off" zones, indicating that more zones should be in the coolant off condition. That one of the coolant on" zones closest to the off"zones in magnitude of strip tension signal is changed to the off" state.

It is also indicated in the above table that excessive bending forces at the roll jacks, either negative or positive, will result in changes of coolant flow. Excessive bending forces occur by virtue of the pressures applied to the jacks 28, 30 and 31 in FIG. 1. If the force exerted by the balance jacks 28 predominates to an excessive degree over the forces in the contour jacks 30 and 31, excessive positive bending force will result. In such a case the coolant should be turned on" in selected zones outside the edge of the strip. On the other hand, if the force exerted by the contour jacks 30 and 31 excessively exceeds the force exerted by the balance jacks 28, resulting in excessive negative bending force, the coolant should be turned off in selected zones outside the edge of the strip. This control of coolant flow to the outside zones is indicated in the table as taking place when the roll jacks are applying forces in accordance with rolling load. As noted above, rolling load control of the roll jack forces is disclosed in Sivilotti et al. application Ser. No. 7 l 3, I50.

Turning now to FIG. 5, signals from the on zones and off" zones discriminators 98 and H00 are applied to the circuit as shown. A signal from the off zones discriminator of FIG. 3 representing the highest off zones discriminator of FIG. 3 representing the highest off" zone voltage generated at the output terminal 132 appears at the same numbered ter- 144 and 182. Additionally, a signal representative of the factor F is applied to an input terminal 230. This signal may be simply a potential representative of the maximum total range of off-flatness that will be tolerated. A signal representative of the factor X is applied to a terminal 232 and may be generated in the same fashion as is the signal F. The signal X represents the difference in the ranges of off-flatness of the coolant on" and coolant off" zones, as explained above.

One of the criteria mentioned above was that total off-flatness should exceed the value F before a change is made. This is accomplished in the circuit of FIG. 5 through the action of a differential amplifier 234 which receives the signal representative of the factor F from the terminal 230 as well as the signal Vmax/off and Vmin/on from the terminals 132 and 182. The differential amplifier generates an output signal only when the difference in the signals from the terminals 132 and 182 exceeds the value of the signal F at the terminal 230. In other words, an output signal is generated by the differential amplifier when the difierence Vmax/off-Vmin/on is greater than F. Vmax/off, of course, represents the highest strip tension sensed for the off" coolant zones and Vmin/on represents the lowest strip tension sensed for the coolant on" zones, i.e., total offpflatness. The signal from the differential amplifier 234 is applied as one input to an AND gate 236.

The AND gate 236 receives a signal from the speed signal source 114 of FIG. 1, an the signal is generated any time the strip speed exceeds S feet per minute. The source 114 may involve, e.g., a tachometer generator (not shown) that monitors the strip speed from the strip mill and generates an output signal whenever the speed exceeds a predetermined value S. It has also been pointed out that an alternative criterion may be its other input signal received from OR gate 262, generates an that a minimum delay time has elapsed since the commence- 1 ment of a rolling operation. In such a case the speed signal" will be replaced by a timing signal only preset after such delay time, the timing signal will not be dependent upon the speed of the speed of the strip.

Another signal to the AND gate 236 is derived from a master/auto switch 238, which is actuated to provide a signal indicating that the system is to be placed under automatic mode of operation. 2

Another input signal to the AND gate 236 is derived from input terminal 240, which is supplied with pulse signals from any suitable clock generator (not shown) for timing control purposes. The pulse signals at the terminal 240 are spaced apart by any desired amount of time.

A further signal is supplied to the AND gate 236 from an input terminal 242 designated cycling time delay." This signal is generated by the system of FIG. 6, to be described below, and is only present at predetermined times following a preceeding change in coolant flows. The cycling time delay signal ensures that a minimum time will elapse following one change in coolant flows before the next change is made.

The comparator input to the AND gate 236 is supplied from an OR gate 244. The OR gate receives signals from a differential amplifier 246 and a comparator network 248. The differential amplifier 246 in. turn receives input signals from the terminals 144 and 194 and generates an output signal that is applied to the OR gate whenever the difference Vmax/on- Vmin/off is greater than zero. In other words, the differential amplifier 246 generates an output signal whenever the highest sensed strip tension for the coolant "on zones is greater than the lowest sensed strip tension for the coolant "off" zones. This is not a proper condition, as noted above, since the strip tension signals of all the off zones should be higher than the signals from the on" zones. Such a signal will energize the OR gate 244 which in turn energizes the AND gate 236 if all the other inputs to that AND gate are energized.

The comparator network 248 receives an X input signal from the input 232 as well as a signal from the differential amplifier 250. The differential amplifier 250 in turn receives input signals from the input terminals 132, 144, 194 and 182. This differential amplifier generates an output signal representative of the difference in ranges of off-flatness of the coolant on and coolant off" zones. This difference signal, designated in FIG. 5 as AVoff-AVon, is representative of the following difference: (Vmax/offVmin/off)-(Vmax/on-V- min/on I The comparator network 248 compares the difference signal representing the difference in ranges of off-flatness with the X signal to generate a signal on an output conductor 252 if the difference exceeds the value +X and a signal on conductor 254 if the difference is less than X. In other words, if the range of off-flatness of the coolant off" zones exceeds the range of off-flatness of the coolant"on" zones by the factor X, a signal is generated on the output conductor 252. On the other hand, if the range of off-flatness of the coolant "off" zones by the factor X, a signal is generated at the conductor 254. Either of these two signals energizes the OR gate 244 which in turn energizes the AND gate 236 when the other input signals supplied to that AND gate are present.

The comparator network 248 also generates to output signals on conductors 256 and 258 depending upon whether the difference signal generated by the differential amplifier 250 is greater than zero or less than zero. If the difference output signal at terminal 264. The output signal is designated an on" trigger pulse since it is used to change some coolant ofi" zone to the "on" condition. Similarly, the signal from the comparator network 248 on the conductor 258, indicating that the range of off-flatness of the "on zones exceeds that range for the "off zones, an AND gate 266 is energized (when that AND gate is also energized by a signal from the OR gate 262) to generate an off trigger pulse at terminal 268.

In other words, the comparator network 248 determines which range of off-flatness predominates. If the off-flatness is greater for the coolant "off" zones, a selected off" zone will be changed to the "on condition. On the other hand, if the range of off-flatness is greater for the coolant on zones, a

selected on zone will be changed to the off" condition. In

this connection the OR gate 262 channels signals from the AND gate 236. The OR gate 262 also receives signals from another AND gate 270. This AND gate is for the purpose of providing a manual override to the system and receives a signal auto preset from a terminal 272. This signal may be generated by any suitable means, and along with the clock pulse signal at the terminal 240 will energize the AND gate 270. The AND gate signal appears through the OR gate 262 to provide energization to the enabling inputs of the AND gates 260 and 266 so that either an on" or an off" trigger pulse will be generated at the output terminals 264 and 268 depending upon which range of off-flatness predominates.

I FIG. 6

to an AND gate 300-2. A signal is present at input terminal 152-2 if, as explained above in connection with FIG. 3, the zone Z is presently in the ofi" condition and is the off" zone having the least sensed strip tension, indicating that this zone should be switched to the coolant on" condition. An on" trigger pulse at terminal 264 (generated by the circuit of FIG. 5) will energize the AND gate 300-2. A signal from the AND gate is applied to an OR gate 302-2, whose output is coupled to the "on" input of a bistable multivibrator 304-2, constituting the control element for zone 2. When triggered to its on" condition, the multivibrator 304-2 generates an output signal on conductor 306-2. The signal on the conductor 306-2 is amplified by a power amplifier 308-2 which in turn controls a solenoid 310-2. The solenoid when energized opens the valve V2 in FIG. 1 supplying coolant to zone Z.

In the on" condition of the bistable multivibrator 304-2, the energized conductor 306-2 activates a coolant indicator 312-2 which indicates the on" or coolant supply condition of the valve VZ. When the signal on the conductor 306-2 changes from off" to on" a transient signal is developed by virtue of capacitive coupling 314-2 which couples the conductor 306-2 to an OR gate 316 (common to all zones). The OR gate in turn controls a monostable multivibrator 318 (also common to all zones) to generate an output signal at the ter- 6 5 minal 242 which is the cycling time delay terminal mentioned above in connection with FIG. 5. The monostable multivibrator is typically in its on condition and, when energized by a signal from OR gate 316, is triggered to its off condition for a predetermined time period, which is the cycling time delay period. Thus, when the conductor 306-2 is switched from off to on indicating that the coolant flow from zone 2 is changed from off" to on," the signal at the terminal 242 goes off" for the off period of the multivibrator 318. The signal will not reappear at the terminal 242 until after the cycling time delay period has elapsed. As mentioned above in connection with FIG. 5, this ensures that no further change can be made following a change in coolant flow for a zone until a predetermined time period is passed. This time delay, however, is only applicable to changes in accordance with a detected strip stress at the billy roll and is not a limitation, for example, when changes are to be made in accordance with excessive bending forces, as will be explained below.

In the event that coolant is currently being supplied to zone 2, and zone Z is to be switched to its condition because of zone Z being the "on" that is experiencing the highest strip tension, an AND gate 320-2 is adapted to be actuated. The AND gate 320-2 receives a signal from terminal 202-2 (from the "on" zones discriminator of FR]. 4). The terminal 202-2 is energized, as explained above in connection with FIG. 4, whenever the zone Z experiences the highest strip tension of the on" zones. Such a signal in conjunction with an oft trigger pulse at the terminal 268 (from the circuit of FIG. 5) will energize the AND gate 320-2 in turn energizing an OR gate 322-2. The signal from the OR gate 322-2 is coupled to the off" input of the bistable multivibrator 304-2. In its oft condition the bistable multivibrator energizes a conductor 324-2 and causes the conductor 306-2 to be deenergized, deenergizing the coolant solenoid 310-2 for zone Z and closing the coolant valve V2. An 011" coolant indicator 326-2 is energized by the conductor 324-2. The capacitively coupled by coupling 328-2 to the OR gate 316 that controls the monostable multivibrator 318. Hence, when the conductor 324-2 becomes energized, indicating a change from the coolant on" to coolant ofP condition, the capacitive coupling from that conductor causes the cycling time delay action to take place preventing a further change in zone Z for the cycling time delay period.

As explained above, whenever excessive bending forces at the roll jacks are encountered during a time when the roll jacks are controlled in accordance with rolling load, the circuit operates to appropriately change the flow of coolant in selected zones outside the edges of the strip. To this end the signals representing excessive negative and excessive positive bending forces at the terminals 94 and 92 (numbered the same as the conductors 94 and 92 from the comparator 90 of FIG. 1) are coupled to AND gates 330-2 and 332-2. Each of these AND gates is also coupled to another AND gate 334-2 which receives two input signals. The first signal is from an automatic roll deflection control input 336-2 which is energized when the roll jacks are automatically controlled in accordance with rolling load, as disclosed, e.g., in Sivilotti et al. application Ser. No. 713,150. Such a signal is developed by the signal source 97 in FIG. 1. The other signal to the AND gate 334-2 is received from an input terminal 338-2. This terminal is designated in FIG. 6 width zone selector (outside zones). This terminal is energized if the zone Z is one of selected zones outside the edge of the strip. An appropriate signal may be developed by any means automatically to energize the terminal 338-2 if it represents an outside zone. A multideck switch (not shown) may be employed having, for example, a deck corresponding to each position of the switch. The switch may have as many positions as strip widths that are encountered. For any particular strip width that is represented by a position of the switch, an appropriate deck is switched into the circuit providing appropriate signals to those terminals 338 representing selected zones outside the edges of the strip.

rieraiimig'raimars hic'luii'e'd 6556i; 5 'rapre easae distribution of zones both inside and outside the edges of the strip for control purposes for various strip widths. It is assumed for the purpose of this example that there are a total of 25 zones across the strip mill rolls that compress the strip.

Mini: 1 [Manually and automatically controlled zones as a function of strip width, assuming 25 zones, strip centered about middle zone 13] Auto Auto Zones controlled controlled Manually Strip width at edge inside outside controlled (in zones) of strip zones zones zones 12, 14 13 1-10 16-25 11, 12 14, 15 ll, 15 12-14 1-9 17-25 10, 11 15,16 10, 16 11-15 1-8 18-25 9, 10 16, 17 9, 17 10-16 1-7 19-25 8, 9 17, 18 8, 18 9-17 1-6 29-25 7, 8 18, 19 7, 19 8-18 1-5 21-25 6, 7 19, 20 6, 20 7-19 1-4 22-25 5, 6 20, 21 5, 21 6-20 1-3 23-25 4, 5 21, 22 4, 22 5-21 1-2 24-25 3, 4 22, 23 3, 23 4-22 1 25 2, 3 23, 24 2, 24 3-23 None 1, 2 24, 25 1, 25 2-24 1 25 zones. The second column gives the zones at the very edge of the strip (it is assumed that the numbering of zones goes from 1 to 25, right to left, as viewed in FIG. 2; it is also assumed that the middle of the strip is positioned in the middle of zone 13). The third column designates the zones inside the edges of the strip that are automatically controlled in accordance with strip tensions for the zones as sensed by the billy roll 70. The forth column designates the outside zones that are automatically controlled in accordance with excessive positive and negative .bending forces. The fifth column designates those zones representing different strip widths. As an example taken from Table I, if the strip is 15 zones wide, zones 7 to 19 are controlled in accordance with sensed strip tension, zones 1 to 4 and 22 to 25 are controlled in accordance with excessive bending force at the roll jacks, and zones 5, 6, 20 and 21 are left to manual control.

Returning to FIG. 6, the signal from the width zone selector energizes the AND gate 334-2 along with the automatic roll deflection control signal. This AND gate, as noted above, controls the two AND gates 330-2 and 332-2. The AND gate 330-2 develops an output signal in the event excessive negative bending force is encountered, while the AND gate 332-2 1 develops an output signal in the event that excessive positive bending force is encountered. The signals from the AND gates 330-2 and 332-2 respectively energize the OR gates 332-2 and 302-2 which control the bistable multivibrator 304-2 to switch that multivibrator either off or on, as the case may be, for excessive bending force. It will be noted that excessive negative bending force causes the multivibrator to be switched off," turning off the flow of coolant to the zone 2, while excessive positive bending force causes the multivibrator to be switched on! (if it is not already on) providing coolant to the zone 2.

The circuit of FIG. 6 also includes a manual on input 340-2 which is energized whenever it is desired to place the zone 2 under manual control and to turn it on." The manual on signal from the terminal 340-2 is coupled through OR gate 302-2 tortum the bistable multivibrator 304-2 on if it is not already in that condition.

Similarly, a manual of signal is provided at a terminal 342-2 in the event that it is desired to place zone 2 under manual operation and in the off condition. Such a signal is coupled through OR gate 322-2 to switch the bistable multivibrator 304-2 to its off" condition, if it is not already in that state, deenergizing the coolant solenoid 310-2.

As noted above, the width zone selector selects outside zones for coolant flow control in accordance with excessive bending forces, as well as inside zones for control of coolant flow in accordance with strip tensions sensed at the billy roll. A suitable signal is generated at terminal 344-2 designated width zone selector (inside zones)." This terminal is energized in the event that the zone 2 is one of the selected zones inside the edges of the strip. A signal from the terminal 344-2 is applied to an AND gate 346-2 as well as to another AND gate 348-2. The other input to the AND gate 346-2 is designated "all on" (terminal 350-2) and is energized whenever it is desired to place all inside" zones in the coolant on condition. The AND gate 346-2 generates a signal applied to the OR gate 302-2 which in turn switches the bistable multivibrator 304-2 into its on" condition if it is not already in that state. This action energizes the coolant solenoid 310-2 providing for the flow of coolant in zone Z to the strip mill rolls.

It was noted above that the width zone selector signal from terminal 344-2 (zone Z is an inside" zone) is applied to AND gate 348-2. The other input to this AND gate is derived from terminal 360-2 designated automatic operation (zone 2)." This terminal is energized whenever zone 2 is to be under automatic operation in accordance with sensed strip tension at the billy roll. The energized AND gate 348-2 triggers a bistable multivibrator 362-2. In its "on" condition the bistable multivibrator 362-2 generates an output signal which is applied to AND gates 364-2 and 366-2. The signal also energizes an indicator 368-2 indicating that zone Z is under automatic operation with respect to strip tension. The two AND gates 364-2 and 366-2 respectively receive other input signals from the off" and on" outputs of the bistable multivibrator 304-2. If the on" output of this latter multivibrator is energized, which is the case when coolant is being supplied to the zone 2, the AND gate 366-2 is energized providing an enabling input signal to an analog AND gate 370-2. This analog AND gate may be a field effect transistor, for example, designed tofprovide an analog output at an output terminal 372-2 of the input signal which is derived from the slip ring 72-2 (FIG. 1). In other words, the input to the analog AND gate 370-2 is the billy roll signal representative of the strip tension at the zone 2. Accordingly, if coolant is being supplied to zone 2, the strip tension signal for this zone is transmitted through the analog AND gate 370-2 to the output 372-2. This output is designated Zone 2 on" and is coupled to the "on" zones discriminator of FIG. 4. This signal is applied to the bases of the appropriate transistors 172-2 and 170-2 in FIG. 4 corresponding to the zone 2.

n the other hand, if coolant is not being supplied to the zone 2, the off output from the bistable multivibrator 304-2 is energized, enabling the AND gate 364-2 to generate an output signal which is applied to analog AND gate 376-2. This analog AND gate may be the same as the analog AND gate 370-2 and also receives the strip tension signal from the billy roll for zone 2. An output signal is developed at output terminal 378-2 which is coupled to the oft zones discriminator of FIG. 3. ln particular, the signal at the terminal 378-2 is coupled to the bases of transistors 120-2 and 122-2 in FIG. 3 corresponding to zone 2.

In this connection the analog AND gates 370-2 and 376-2 together correspond to one of the signal gates of FIG. 1 (specifically signal gate 2) to channel the billy roll strip tension signal for zone 2 either to the on" zones discriminator 98 or to the off zones discriminator 100, depending upon whether or not coolant is being supplied to the zone 2.

Referring again to FIG. 6, the width zone selector input 344-2 ("Inside" zone) is coupled to the automatic operation input 360-2 by a capacitive coupling network designated 380-2. The capacitive coupling network provides an output signal whenever the width zone selector is changed from a condition in which zone 2 is not an inside zone to a condition in which zone 2 is an "inside zone. Whenever zone 2 is changed to an inside" zone, a signal appears at the width zone selector input terminal 344-2. The capacitive coupling network 380-2 provides a pulse signal at the terminal 360-2. This pulse input signal from the capacitive coupling network as well as the width zone selector signal itself from the terminal 344-2 together energize the AND gate 348-2 so as to switch the bistable multivibrator 362-2 from its "off" to its "on" condition. In this fashion, the coolant control system for a zone is automatically placed into automatic operation in accordance with strip tension whenever the width zone selector is changed to include that zone as an inside zone (inside the edges of the strip and dictating automatic operation).

It should be noted in FIG. 6 that an OR gate 382-2 is also included, supplied with input signals from an inverter 384-2 and from the manual on" and manual oft inputs 340-2 and 342-2. Whenever zone 2 is on the strip edge or is one of the "outside" zones, the signal disappears from input terminal 344-2, causing a signal to be generated at the output of the inverter 384-2. In the event that zone 2 is placed under manual operation, resulting in a signal appearing at either one of the inputs 340-2 and 342-2, or zone 2 is on or outside the edge of the strip, the OR gate 382-2 is energized providing an output signal to the bistable multivibrator 362-2, turning that multivibrator oft and deenergizing the output conductor from the on" output of that multivibrator. In such a case the AND gates 364-2 and 366-2 are deenergized, which in turn disable the analog AND gates 370-2 and 376-2, preventing strip tension signals from the billy roll from being applied to the terminals 372-2 and 378-2. The lack of strip tension signals to the "on" and to the off zones discriminators 98 and 100 prevents automatic operation of the coolant valve corresponding to zone 2.

SUMMARY A representative embodiment of the invention has been described above in connection with the control of the supply of heat exchange medium to a plurality of zones across the rolls of a strip mill. One or more rolling mill or strip conditions are sensed and utilized to control the supply of heat exchange medium to the various zones. In the embodiment described coolant flows outside the edges of the strip are regulated in accordance with excessive bending forces at the roll jacks, coolant flows inside the edges of the strip are regulated in accordance with strip contour at the corresponding zones, and zones at the edge of the strip are manually controlled. A manual override feature has been provided for all zones. The system automatically accounts for a change in the status of a zone, e.g., a change from outside the edges of a strip to inside the edges of a strip. Control in accordance with a sensed condition, e.g., strip tension as detected by a billy roll, is such that extremes in conditions are corrected. In the embodiment shown, maximum and minimum strip tensions for coolant on" and coolant off zones are detected, and changes are made in accordance with the difference of the extremes, with changes made in coolant flows to the extreme zones. Control could be made dependent upon the number of zones that are either on" or off or both.

I claim:

1. In a method of rolling strip utilizing strip mill rolls, in

.which at least one condition of the rolling process is sensed,

and in which the thermal crowns of a plurality of zones across said rolls are varied in accordance with said sensed condition, the improvement comprising the machine operable steps of selectively controlling the thermal crowns of said zones in accordance with at least one of the following criteria:

a. the locations of zones with respect to their positions inside or outside the edges of a strip;

b. the extremes of strip contour variations for selected zones;

c. when a heat exchange medium is supplied to the rolls to control thermal crown, control discriminating between on zones to which said medium is being supplied and otf" zones to which no medium is being supplied.

2. A method as defined in claim 1, in which the thermal crowns of zones corresponding to positions inside the edges of the strip are controlled.

3. A method as defined in claim I, wherein the thermal crowns are varied in. accordance with the difference between the extremes of contour variations.

4. A method as defined in claim 1, wherein the supply of heat exchange medium is varied in accordance with the criterion that the difference between the extremes of contour variations for on" zones exceeds the difi'erence between the extremes of contour'variations for off" zones.

5. A method as defined in claim 4, in which the supply of heat exchange medium in an on" zone is terminated in response to said criterion.

6. A method as defined in claim 5, in which the supply of heat exchange medium is terminated in that one of the on" zones corresponding to an extreme of contour variation.

7. A method as defined in claim 1, wherein the supply of heat exchange medium is varied in accordance with the criterion that the difference between the extremes of contour variations for off zones exceeds the difference between the extremes of contour variations for on" zones.

8. A method as defined in claim 7, in which the supply of heat exchange medium is commenced in an off" zone in response to said criterion.

9. A method asdefined in claim 8, in which the supply of heat exchange medium is commenced in that one of the "off" zones corresponding to an extreme of contour variation.

10. A method as defined in claim I, in which the strip is passed from the strip mill rolls against a billy roll which generates strip tension signals representative of the stresses created in the billy roll by the strip for zones in the billy roll corresponding to said zones across the rolls, and flows of coolant to said zones of said rolls are varied in accordance with said strip tension signals.

11. A method as defined in claim 10, in which the flows of coolant are varied in accordance with extremes of selected ones of said strip tension signals.

12. A method as defined in claim 11, in which the flows of coolant are varied in accordance with the difference between the extremes of the strip tension signals for the coolant "on" zones to which coolant is being supplied and the difference between the extremes of the strip tension signals for the coblant off zones to which no coolant is being supplied.

13. A method as defined in claim 12, in which coolant flow is commenced in that one of the coolant off zones for which a minimum strip tension signal is generated provided that the difference between the extremes of the strip tension signals for the coolant off" zones exceeds the difference between the extremes of the strip tension signals for the coolant on" zones.

14. A method as defined in claim 12, in which coolant flow is terminated in that one of the coolant "on" zones for which a maximum strip tension signal is generated provided that the difference between the extremes of the strip tension signals for the coolant on zones exceeds the'difierence between the extremes of the strip tension signals for the coolant off zones.

15. A method as defined in claim 12, in which the flows of coolant are varied in accordance with the difference between the maximum strip tension signal of the coolant off" zones and the minimum strip tension signal of the coolant on" zones.

16. A method as defined in claim 12, in which the flows 'of coolant are varied in accordance with the difference between the maximum strip tension signal of the coolant "on" zones and the minimum strip tension signal of the coolant off zones.

17. A method as defined in claim 1, wherein no changes are made in the thermal crowns until the passage of a predetermined time from a preceding change.

18. A method as defined in claim 1, in which roll jacks are employed applying forces to the ends of the strip mill rolls, and in which thermal crowns are varied in accordance with excessive forces at the roll jacks.

19. A method as defined in claim 18, in which a heat exchange medium is supplied to zones corresponding to positions outside the edges of the strip in accordance with excessive forces at the roll jacks.

20. A method as defined in claim 19, in which the supply of heat exchange medium to all zones wholly outside the edges of the strip except for those outside zones adjacent the edges of the strip is controlled in accordance with excessive forces at the roll jacks. I

21. A method as defined in claim 19, in which the strip mill rolls include work rolls that bear against a strip that is rolled and backup rolls that bear against the work rolls, and including contour jacks that apply bending forces between the ends of adjacent work and backup rolls and balance jacks that apply bending forces between the ends of adjacent work rolls, wherein zones outside the edges of the strip are supplied with a coolant in response to the condition in which the forces of the balance jacks exceed the forces of the contour jacks by more than a predetermined amount.

22. A method as defined in claim 19, in which the strip mill rolls include work rolls that bear against a strip that is rolled and backup rolls that bear against the work rolls, and including' contour jacks that apply bending forces between the ends of adjacent work and backup rolls and balance jacks that apply bending forces between the ends of adjacent work rolls, wherein the heat exchange medium is a coolant, and zones outside the edges of the strip have the flows of coolant thereto shut off in response to the condition in which the forces of the contour jacks exceed the forces of the balance jacks by more than a predetermined amount.

23. A method as defined in claim 1, in which the strip is passed from the strip mill rolls against a billy roll which generates strip tension signals representative of the stresses created in the hilly roll by the strip for zones in the hilly roll corresponding to said zones across the rolls, the strip tension signals are sensed for said zones, ro'll jacks are employed applying forces to the ends of the strip mill rolls, negative and positive bending forces at the roll jacks are sensed, and in which coolant is supplied to said roll zones in accordance with the following table of operating logic:

OPERATING LOGIC Total off-flatness, as represented by the difference between extremes of the strip tension signals, exceeds a predetermined value F.

Conditions The highest strip tension of the coolant on" zones is greater than the lowest strip tension of the coolant off zones, or thedifference between the ranges of off-flatness of the on" and off" zones, as represented by the difference between extremes of the strip tension signals of the on" and oft zones, exceeds X.

A previous change has not been made within a cycling time delay period.

A zone in which a change is to be made is inside the edge of the strip.

Action Change from coolant "off to coolant on" in that coolant off" zone experiencing the least strip tension if the range of off-flatness in the coolant off" zones exceeds the range of off-flatness in the coolant on zones; or change from coolant on" to coolant off in that coolant 'on" zone experiencing the greatest strip tension if the range of off-flatness in the ebblant on" zones exceeds the range of off-flatness in the coolant oft zones.

Condition Excessive negative bending force at the roll jacks.

Action I I Turn coolant off in selected zones outside the edge of the strip.

Condition Excessive positive bending force at the roll jacks.

Action Turn coolant "on" in selected zones outside the edge of the strip.

24. In apparatus for rolling strip, including strip mill rolls, means for sensing at least one condition of the rolling process, and controllable means for supplying a heat exchange medium to a plurality of zones across said rolls, the improvement comprising means for selectively controlling the supply of said medium in accordance with at least one of the following criteria:

a. the location of zones with respect to their positions inside or outside the edges of a strip;

b. The extremes of strip contour variations for selected zones;

c. on zones to which said medium is being supplied and off" zones to which no medium is being supplied.

25. Apparatus for rolling strip, including strip mill rolls, comprising means for sensing at least one condition of the rolling process, means for supplying a heat exchange medium to a plurality of zones across said rolls and means for individually varying the supply of heat exchange medium to a plurality of said zones in accordance with said sensed condition, wherein roll jacks are employed applying forces to the ends of the strip mill rolls, and in which the condition sensing means comprises means for detecting excessive forces at the roll jacks greater than a predetermined force.

26. Apparatus as defined in claim 25, wherein said varying means varies the supply of heat exchange medium to zones corresponding to positions outside the edges of the strip.

27. Apparatus as defined in claim 24, in which said sensing means comprises a billy roll which generates strip tension signals representative of the stresses created in the billy roll by the strip for zones in the billy roll.

28. Apparatus as defined in claim 27, wherein said control means varies the supply of heat exchange medium to zones inside the edges of the strip.

29. Apparatus as defined in claim 28, in which said control means varies the supply of heat exchange medium in accordance with extremes of said strip tension signals.

30. Apparatus as defined in claim 29, in which said control means varies the supply of heat exchange medium in accordance with the extremes of the strip tension signals for both the on zones to which heat exchange medium is being supplied and the off zones to which no heat exchange medium is being supplied.

31. Apparatus as defined in claim 30, including pulse generating means for generating timing pulses, and including means for initiating changes in the supply of heat exchange medium upon the occurrence of said timing pulses.

32. Apparatus as defined in claim 31, including means for preventing a change in the supply of heat exchange medium within a predetermined time from a preceding change.

33. Apparatus as defined in claim 28, including roll jacks for applying forces to the strip mill rolls, and means for varying the supply of heat exchange medium to zones outside the edges of the strip in accordance with excessive forces applied to the roll jacks greater than a predetermined force.

34. Apparatus as defined in claim 33, in which the strip mill rolls include work rolls that bear against a strip that is rolled and backup rolls that bear against the work rolls, and including contour jacks that apply bending forces between the ends of adjacent work and backup rolls and balance jacks that apply bending forces between the ends of adjacent work rolls, said control means providing cooling of zones outside the edges of the strip in response to the condition in which the forces of the balance jacks exceed the forces of the contour jacks by more than a predetermined amount.

35. Apparatus as defined in claim 33, in which the strip mill rolls include work rolls that bear against a strip that is rolled and backup rolls that bear against the work rolls, and including contour jacks that apply bending forces between the ends of adjacent work and backup rolls and balance jacks that apply bending forces between the ends of adjacent work rolls, said control means providing heating of zones outside the edges of the strip in response to the condition in which the forces of the contour jacks exceed the forces of the balance jacks by more than a predetermined amount.

36. Apparatus as defined in claim 27, wherein the heat exchange medium is a coolant, and the control means varies the flows of coolant to zones inside and outside the edges of the strip as set forth in the following table of operating logic:

OPERATING LOGIC Total off-flatness, as represented by the difference between extremes of the strip tension signals, exceeds a predetermined value F.

Conditions The highest strip tension of the coolant "on zones is greater than the lowest strip tension of the coolant off zones, or the difference betweenthe ranges of off-flatness of the on" and off" zones, as represented by the difference between extremes of the strip tension signals of the on and off" zones, exceeds X.

A previous change has not been made within a cycling time delay period.

A zone in which a change is to be made is inside the edge of the strip.

Action Change from coolant off" to coolant on" in that coolant off zone experiencing the least strip tension if the range of off-flatness in the coolant off" zones exceeds the range of off-flatness in the coolant on zones; or change from coolant on" to coolant off in that coolant on zone experiencing the greatest strip tension if the range of off-flatness in the coolant "on zones exceeds the range of off-flatness in the coolant oft zones.

Condition Excessive negative bending force at the roll jacks.

Action Turn coolant off in selected zones outside the edge of the strip.

Condition Excessive positive bending force at the roll jacks.

Action Turn coolant on in selected zones outside the edge of the strip.

37. In a control system in which a condition is sensed for each of a plurality of zones and a first or a second action is taken for each of the zones tending to change that condition, the combination of means for classifying the zones into a first group in which the first actionis being taken and into a second group in which the second action is being taken, means for detecting the extremes of the sensed condition for the zones in each of the two groups, and means for varying the action taken in one or more of the zones to change the classification of the zone from one group to the other in accordance with the detected extremes of the sensed condition.

38. Apparatus as defined in claim 37, wherein the varying means is active when the difference between the extremes of the sensed condition of zones in the first group differs by greater than a predetermined amount from the difference between the extremes of the sensed condition of zones in the second group.

39. Apparatus as defined in claim 38, wherein said varying means includes means for changing the action taken in a zone exhibiting an extreme of the sensed condition.

40. Apparatus as defined in claim 39, wherein said varying means changes the action taken in said zone exhibiting said extreme of the sensed condition for that zone belonging to the group in which the difference between detected extremes is greater.

41. Apparatus as defined in claim 40, wherein the varying means changes the action taken in that zone in which the value of the sensed condition is closest to the values of the sensed condition of zones of the other group.

42. Apparatus as defined in claim 37, wherein the varying means is active when the range defined by the difference between the extremes of the sensed condition of zones in the first group overlaps the range defined by the difference between the extremes of the sensed condition of zones in the second group.

43. Apparatus as defined in claim 42, wherein the varying means is only active if the total range of the two groups combined is greater than a predetermined amount.

44. Apparatus as defined in claim 37, wherein the varying means acts to change the actions taken in the zones so that the zones in the first group of zones ultimately exhibit conditions which range over values less than the values over which the detected conditions of the zones in the second group range.

45. In a method of controlling a system in which a condition is sensed for each of a plurality of zones and a first or a second action is taken for each of the zones, the steps of classifying the zones into a first group in which the first action is being taken and into a second group in which the second action is being taken, detecting the extremes of the sensed condition for the zones in each of the two groups, and varying the action taken in one or more of the zones to change the classification of the zone from one group to the other in accordance with the detected extremes of the sensed condition.

46. A method as defined in claim 45, wherein the action taken in one or more of the zones is changed when the difference between the extremes of the sensed condition of zones in the first group difiers by greater than a predetermined amount from the difference between the extremes of the sensed condition of zones in the second group.

47. A method as defined in claim 46, including changing the action taken in a zone exhibiting an extreme of the sensed condition.

48. A method as defined in claim 47, wherein the action is changed in said zone exhibiting said extreme of the sensed condition for that zone belonging to the group in which the difference between detected extremes is greater.

49. A method as defined in claim 48, wherein the action is changed in that zone in which the value of the sensed condition is closest to the values of the sensed condition of zones of the other group.

50. A method as defined in claim 45, wherein the action taken in one or more of the zones is changed when the range defined by the difference between the extremes of the sensed condition of zones in the first group overlaps the range defined by the difference between the extremes of the sensed condition of zones in the second group.

51. A method as defined in claim 50, wherein the action taken in one or more of the zones is changed only if the total range of the two groups combined is greater than a predetermined amount.

52. A method as defined in claim 45, wherein the actions taken in the zones are changed so that the zones in the first group of zones ultimately exhibit conditions which range over values less than the values over which the detected conditions of zones in the second group range.

53. A method as defined in claim 1, in which control is in accordance with all three criteria (a), (b) and (c).

54. Apparatus as defined in claim 24, in which said control means effects control in accordance with all three criteria (a), (b) and (c). v

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,587,265 28 June 1971 Olivo G. Sivilotti Patent No. Dated Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Correct the name of the assignee from "Alcon" to -Alcan- Column 1, line 2 after "rolls", "in" should be -is--;

line 29, after "coolant is", "current" should be -currently-;

Column 3, line 7, after "The", "bill" should be --billyline 22, after "V1, V2, .n" should be Column line 17, after "March 1 4, 1968," insert -patent-;

Column 5, line 69, after "136-2. "l3 4C-n" should be l3 i-n--;

Column 7, line 49, after "is" "here" should be -higher--;

Column 10, line 5, after "degree" "of" should be for--;

lines 15 and 16, after "zones" delete "and if the range of";

lines 45 and U6, delete "zones discriminator of FIG. 3 representing the highest 'of'" Column 11, line 1 4, after "time," insert and-- line 15, delete "the speed of" line 33, "comparator" should be -remaining--; line 71, "to" should be -two-- Column 13, line 11, after "'on'" insert -zone--;

line 26, after "The" insert -conductor 32 4-Z is also--;

Column 1 4, Table I, Zones," line 5 (from start under title "Auto Controlled Outside of that column) "29" should be Signed and sealed this 5th day of December 1972.

(SEAL) Attest:

EPV I ARD M.FLETCHER ,JR. ROBERT GOTTSCHALK finmmissinnen nf EBJZQIWS 

